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Glossary · Energy industry & energy transition

Common Information Model

Common information model CIM electricity grid Data model grid operation Digitalisation IEC

The Common Information Model, CIM for short, is a standardised, abstract information model for electrical power supply systems. It describes how equipment and other objects of a power system are represented in a uniform way: network nodes, lines, transformers, switching devices, measurement points, generation plants, loads, schedules and market objects. CIM is neither software nor a database. It is a shared technical language for data about the power grid and the adjacent business processes. The standard speaks of an abstract model that represents all the main objects of an electric utility that typically occur in operation. The German version of the standard calls it "Allgemeines Informationsmodell" (General Information Model). Note: under the same name there is a different, unrelated standard in IT systems management. In this glossary, the model of the electricity industry is always meant.

Standards and structure

CIM is maintained in Technical Committee 57 of the International Electrotechnical Commission (IEC) and is spread across three series of standards. The core is IEC 61970-301, the CIM base model. Historically it comes from the world of control systems for the transmission grid (Energy Management Systems, EMS), but today it is used jointly by all parts. In Germany, DIN EN IEC 61970-301:2025-03 currently applies, which is based on IEC 61970-301:2020 with Amendment 1 of 2022. IEC 61968-11 supplements the base model with packages for distribution grids and for connection to enterprise-wide systems, such as asset management, work orders, customers, load control and metering. IEC 62325-301 extends the model by the data that participants in electricity markets exchange. The division of labour whereby IEC 61970 stands for transmission, IEC 61968 for distribution and IEC 62325 for markets is therefore only a rough rule of thumb. The standards emphasise that behind all the individual documents there is a single, coherent information model.

Objects, attributes and relationships

Technically, CIM consists of classes, attributes and relationships. They are described in the modelling language UML. A line in CIM is thus not merely a name in a table. It is an object with electrical parameters, it belongs to a voltage level and it is linked to connectivity nodes via terminals. A circuit breaker is a piece of equipment with terminals and a switching state. Depending on whether it is open or closed, it separates or connects parts of the network in the calculation. Only through such relationships does data become usable for load flow calculation, state estimation or short-circuit calculations.

The topology is particularly important. For a network calculation, it is not enough to know which assets exist. What matters is how they are electrically connected and which switching state currently applies. CIM therefore separates the physical structure made up of equipment, terminals and connectivity nodes from the operational topology calculated from it. The latter depends on which switches are currently open or closed. Put simply: the structure shows where cables are laid. The calculated topology shows where current can actually flow at the moment.

Model, profile and exchange format

CIM is often confused with a file format. The standard, however, separates three levels:

  • The information model according to IEC 61970-301, IEC 61968-11 and IEC 62325-301 defines terms and their meaning.

  • Profiles select a subset of the overall model for a specific purpose, restrict it and define mandatory fields.

  • Exchange formats govern the technical representation. For network models, this is above all CIMXML according to IEC 61970-552. It uses the CIM RDF schema from IEC 61970-501 and builds XML documents on it. CIMXML is modelled on RDF/XML but is stricter: it allows only a simplified syntax and therefore cannot simply be equated with arbitrary RDF/XML. Messages between applications, for example according to IEC 61968 or in the market domain, are usually described with XML schemas.

An exchange format can be changed without losing the technical meaning. Conversely, the most modern format helps little if the partners interpret terms, units and object relationships differently.

CGMES in the European transmission grid

The most important CIM profile in Europe is the Common Grid Model Exchange Standard (CGMES) of ENTSO-E, originally called the Common Grid Model Exchange Specification. Via CGMES, the transmission system operators exchange network models for operational planning and network development. Each operator supplies a model of its area of responsibility, and a common European network model is built from these individual models. According to the IEC, CGMES covers modelling for load flow, short-circuit and dynamics calculations and additionally permits the exchange of diagrams and geodata.

On the version status: CGMES 2.4.15 was published in 2017 as IEC Technical Specification TS 61970-600-1/-2. Since 2021, CGMES 3.0 has been standardised as IEC 61970-600-1/-2:2021, and ENTSO-E lists the 2017 versions as superseded. In operation, older and newer versions may be used side by side for a time. Which version applies to a particular exchange must therefore be clarified case by case.

Significance in the distribution grid and in market processes

The importance of CIM is growing because grid operation depends more and more on data. Network models traditionally reside in control systems, geodata in GIS applications, master data in asset management systems, measured values in separate databases and market information in communication systems. This becomes a problem as soon as the same piece of equipment must be described identically in several processes. A transformer that has a different name in planning than in the control system becomes a source of error when an automated calculation uses both sources.

Distribution system operators have very many assets but historically fewer real-time measurements than transmission system operators. At the same time, photovoltaics, heat pumps, charging infrastructure and controllable consumption devices are being added. Anyone who wants to assess connection requests, find bottlenecks or evaluate flexibility needs consistent data on network structure, installations, measurement points and customer connections. The distribution extensions in IEC 61968 cover, among other things, unbalanced medium- and low-voltage networks as well as distributed generation plants. CIM does not solve these tasks itself. But it can provide the common data basis for applications such as an ADMS.

Market processes also refer to network objects: schedules, balancing, capacity allocation and congestion management. IEC 62325 contains, among other things, a profile for the European electricity market. If a market area, a grid connection point or a generation unit is described differently in different systems, coordination effort arises. One restriction applies here: German market communication between suppliers, network operators and metering point operators has so far run predominantly via its own, non-CIM-based formats.

What CIM is not

Standardisation does not automatically create interoperability. The standards are extensive, and practical applications use profiles. Two systems may both formally use CIM and still work with different profile versions, extensions or mandatory fields. Cooperation works only when model, profile, validation rules, versioning and technical agreements fit together. ENTSO-E therefore operates its own conformity assessment procedure for CGMES.

CIM is also not a ready-made digital twin. The model can specify that a transformer has a rated power, a voltage level and certain connection nodes. But it cannot guarantee that these values are entered correctly and kept up to date. Introducing CIM is therefore not a purely IT project. The specialist departments must clarify which system is authoritative for which objects, how changes are approved, how historical data is handled and how detailed a network model should be. A transmission network model needs different details than a model for a low-voltage network.

Economically, CIM pays off above all where interfaces, data cleansing and manual coordination cause a great deal of effort. At first, however, the changeover, training and data maintenance themselves cost money. The benefit becomes apparent only when recurring data exchanges run more stably and new applications can be connected more easily.

For the digitalisation of the power system, this delimitation is central. A measured value says little without reference to the measurement point, equipment, timestamp and network configuration. CIM describes the objects to which measured values and calculations refer. However, it does not decide whether network operators must disclose data, which data protection rules apply or who pays for data quality. These questions belong to regulation and corporate governance. In short: CIM is the standardised descriptive language that makes network data compatible between technical and energy-industry applications. But it replaces neither well-maintained data nor clear responsibilities.

Sources

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Edited by eCMS on 11.11.2026 17:51

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